Newcastle disease virus--some properties of Australian strains.

Seventeen Australian strains of Newcastle disease virus were tested for their biological properties: mean death time, heat stability of the hemagglutinin and infectivity of the virus at 56 C, the elution time of virus from chicken erythrocytes, and the ability to hemagglutinate equine red blood cells. The strains differed considerably in their reactions. All had mean-death-time indices of 112 or greater, indicating that all were lentogenic. Strains were identified that had heat-labile and -stable hemagglutinin and infectivity, slow and fast elution, and variable ability to agglutinate equine erythrocytes. The significance of the results is discussed in terms of their usefulness in identifying exotic strains of the virus.